This invention relates to a chemical feeding device and more particularly to an apparatus for feeding a concentrated chemical solution developed from a solid chemical material into a stream of flowing liquid.
Various types of apparatus have been used as chemical feeders, but most of these suffer from a number of deficiencies. This is especially true if the external hydraulic conditions into which the feeding operation takes place vary, namely, the pressure, flow rate and constancy of flow. Many of the proportional fluid feeders currently available operate on the principle of the aspirator--fluid flow perpendicular to an orifice creating suction through the orifice--or on the principle of displacement and turbulent mixing. While in some instances these work well after steady state conditions are established in constant flow systems, in changing systems steady state conditions may never be established. This results in random or at least erratic feed levels.
Some of the problems that occur, for example, are that in aspirator designs there is a plugging up with solid debris at the aspiration orifice because the orifice must be small enough to balance the high concentration of the solution being fed. Screens and filters which are fine enough to prevent clogging would also interfere with the suction.
Turbulent displacement designs often are defective in that the internal flow rate must be sufficiently high to promote turbulent mixing. That in turn requires that the solid chemical which dissolves to produce the concentrated feed solution must be able to dissolve very quickly in order to keep pace with the internal flow rate.